The effect of nitrogen management on seed yield and quality in traditional and canola-quality white mustard

The article presents the results of a three-year field study that was conducted in Poland to evaluate the yield and quality of seeds and oil from traditional (SAM) and canola-quality white mustard (SAC) in response to different N fertilizer rates (0, 40, 80, 120, and 160 kg ha–1). Seed yields were 25% higher in SAM than SAC. The seeds of SAC contained more crude fat (by 3%) and crude fiber (by 6%) than the seeds of SAM. In turn, the seeds of SAM were a richer source of total protein (by 7%). The content of glucosinolates (GSLs) was 8–10 times lower in the seeds of SAC than SAM. The seeds of both mustard cultivars were most abundant in γ-tocopherol (γ-T) (90–94%). The seeds of SAC were characterized by a higher content of γ-T and a lower α-T/γ-T ratio than SAM seeds. White mustard oil contained mostly MUFAs (69–75%). However, C22:1 accounted for more than 50% of MUFAs in the oil SAM. In the oil SAC, the proportion of C22:1 did not exceed 6%, whereas C18:1 accounted for nearly 85% of total MUFAs. Nitrogen fertilization induced a significant increase in seed yields (by 33%), a decrease in crude fat content (by 3–4%), and an increase in total protein content (by 4%), and crude fiber content (by 7%). Nitrogen decreased GSL levels by 31% in SAM seeds. In SAC, N fertilization induced differences in the qualitative composition of GSLs, but did not affect the total GSL content of seeds. Higher N rates increased the content of α-T and γ-T, the α-T/γ-T ratio, and total T content. Nitrogen fertilization decreased the content of C18:3 in the seeds of the SAM. In SAC, the application of N decreased the content of C18, C18:1, and C18:3, and increased the biosynthesis of C18:2, C20:1, and C22:1.